The teachers union boss and City Council Speaker Gifford Miller have joined a lawsuit to toss out the high-stakes third-grade English test because of snafus that occurred when they were administered.

Miller and UFT chief Randi Weingarten pointed to the fact that some kids got an advance peek at some questions before the original test, and that there was conflicting information on last week’s makeup exam.

“It is ridiculous and it points out how absurd the policy was in the first place,” said Miller, who wants to run for mayor.

Miller opposed Mayor Bloomberg’s policy of ending social promotion in the third grade by largely determining whether a student advances based on results of standardized English and math exams.

Weingarten argued that the mistakes make the results invalid and unreliable. “If you really believe in high standards and tests that measure them, then those tests have to be 100 percent reliable and 100 percent fair,” said Weingarten.

But Schools Chancellor Joel Klein’s office issued a statement saying “only a small number of students” were affected by the snafus, and the results will be examined to see if there were any disparities.